U.S. patent number 6,518,366 [Application Number 09/937,901] was granted by the patent office on 2003-02-11 for nitrile group-containing fluoroelastomer and preparation process of same.
This patent grant is currently assigned to Daikin Industries, Ltd.. Invention is credited to Masaki Irie, Kazuyoshi Kawasaki, Mitsuru Kishine.
United States Patent |
6,518,366 |
Irie , et al. |
February 11, 2003 |
Nitrile group-containing fluoroelastomer and preparation process of
same
Abstract
To provide a solid fluoroelastomer having nitrile group at the
end which gives a crosslinked product being excellent in heat
resistance, solvent resistance, chemical resistance, compression
set and cleanliness, and an economical process for preparation
thereof. The process for preparing a nitrile group-containing
fluoroelastomer by converting amide group contained in a polymer
molecular chain of a solid fluoroelastomer into nitrile group in
the presence of a dehydrating agent.
Inventors: |
Irie; Masaki (Settsu,
JP), Kawasaki; Kazuyoshi (Settsu, JP),
Kishine; Mitsuru (Settsu, JP) |
Assignee: |
Daikin Industries, Ltd. (Osaka,
JP)
|
Family
ID: |
14089021 |
Appl.
No.: |
09/937,901 |
Filed: |
October 1, 2001 |
PCT
Filed: |
March 28, 2000 |
PCT No.: |
PCT/JP00/01913 |
PCT
Pub. No.: |
WO00/59959 |
PCT
Pub. Date: |
October 12, 2000 |
Foreign Application Priority Data
|
|
|
|
|
Mar 31, 1999 [JP] |
|
|
11-093676 |
|
Current U.S.
Class: |
525/326.2;
525/326.4; 525/359.3; 525/378; 525/379 |
Current CPC
Class: |
C08F
8/00 (20130101); C08F 8/30 (20130101); C08F
8/00 (20130101); C08F 214/18 (20130101); C08F
8/30 (20130101); C08F 214/18 (20130101) |
Current International
Class: |
C08F
8/00 (20060101); C08F 8/30 (20060101); C08F
008/18 () |
Field of
Search: |
;525/326.2,326.4,359.3,378,379 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lipman; Bernard
Attorney, Agent or Firm: Sughrue Mion, PLLC
Claims
What is claimed is:
1. A process for preparing a fluoroelastomer having nitrile group
by converting, in the presence of a dehydrating agent, amide group
contained in a polymer molecular chain of a solid fluoroelastomer
into nitrile group.
2. The preparation process of claim 1, wherein the dehydrating
agent is in the form of gas or liquid.
3. The preparation process of claim 2, wherein the dehydrating
agent is COF.sub.2.
4. A nitrile group-containing fluoroelastomer which is in the form
of solid, has nitrile groups at both ends and is represented by the
formula (I):
wherein R.sub.f is a divalent fluoroelastomer chain.
5. The nitrile group-containing fluoroelastomer of claim 4, wherein
the fluoroelastomer chain R.sub.f is a perfluoroelastomer chain of
a copolymer or terpolymer represented by the formula (1): ##STR14##
wherein m/(n+p) is 95 to 50/5 to 50, n/p is 0/100 to 100/0, m+n+p
is from 100 to 10,000, R.sub.f.sup.1 is a perfluoroalkyl group
having 1 to 8 carbon atoms, R.sub.f.sup.2 is --(CF.sub.2
CFYO).sub.q R.sub.f.sup.3, in which R.sub.f is a perfluoroalkyl
group having 1 to 6 carbon atoms, Y is fluorine atom or
trifluoromethyl group, q is an integer of 1 to 5, or
a perfluoroelastomer chain of a terpolymer or tetrapolymer
represented by the formula (2): ##STR15## wherein 1/m/(n+p) is 95
to 35/0 to 30/5 to 35, n/p is 0/100 to 100/0, 1+m+n+p is from 100
to 10,000, R.sub.f.sup.1 and R.sub.f.sup.2 are as defined
above.
6. A fluoroelastomer composition comprising a solid nitrile
group-containing fluoroelastomer which has end nitrile groups in
the number of more than 1/2 of the total number of end groups of
molecular chains of the fluoroelastomer.
Description
TECHNICAL FIELD
The present invention relates to a nitrile group-containing
fluoroelastomer having nitrile group in a molecular chain,
particularly at the end of the molecular chain and a process for
preparation thereof. The elastomer can give a crosslinked product
having a very good sealing property, mechanical strength and ultra
high heat resistance of not less than 300.degree. C.
BACKGROUND ART
Fluoroelastomers comprising a fluoromonomer unit as a recurring
unit such as tetrafluoroethylene (TFE) are used widely as a sealing
material to be used under strict environment since they exhibit
excellent chemical resistance, solvent resistance and heat
resistance. Particularly in the fields of aviation and space
industries, semi-conductor production apparatuses and chemical
plants, which are major applications of the fluoroelastomers, heat
resistance of sealing at 300.degree. C. or more is demanded.
Such a crosslinked product having excellent heat resistance is
obtained by firstly preparing a nitrile group-containing
fluoroelastomer having nitrile group in a molecular chain as a cure
site by copolymerizing perfluoro(vinyl ether) (CNVE) having nitrile
group with TFE and perfluoro(alkyl vinyl ether) (PAVE) and then
crosslinking the fluoroelastomer by triazine crosslinking with
organotin, oxazole crosslinking with a bisaminophenol compound or
tetraamine compound or imidazole crosslinking, as described, for
example, in JP-A-58-152041 and JP-A-59-109546.
However CNVE for introducing nitrile group as a cure site requires
a long synthesis step and is very expensive, and also the nitrile
group in the obtained nitrile group-containing fluoroelastomer is
unstable. Further a mechanical strength and sealing property at
high temperature (compression set) of the obtained crosslinked
product are insufficient.
The inventors of the present invention have made various studies
with respect to conventional nitrile group-containing
fluoroelastomers and assumed that a reason why sufficient
properties were not obtained was the fact that nitrile cure site
group is present only as a pendant of a molecular chain. Thus the
inventors have studied introduction of nitrile group into an end of
the molecular chain. However in a conventional method described in
Polymer Journal, Vol. 17, No. 1, pp 253 to 263, in which a solid
dehydrating agent such as phosphorus pentoxide is used (Formula 10
at page 261), it is possible to carry out conversion of an end
group of liquid fluorooil into nitrile group but a solid
fluoroelastomer cannot be dehydrated uniformly and the dehydrating
agent remains in the obtained product. Therefore an intended solid
fluoroelastomer having nitrile group at the end could not be
obtained.
An object of the present invention is to provide a solid
fluoroelastomer having, at the end, nitrile group functioning as a
cure site, and an economical preparation process thereof.
Another object of the present invention is to provide a novel
synthesis process for converting amide group into nitrile group,
and a dehydrating agent to be used therefor.
DISCLOSURE OF INVENTION
The present invention relates to a process for preparing a nitrile
group-containing fluoroelastomer by converting amide group
contained in a polymer molecular chain of a solid fluoroelastomer
into nitrile group in the presence of a dehydrating agent.
It is preferable that the dehydrating agent to be used is in the
form of gas or liquid. Particularly COF.sub.2 is preferable.
The solid nitrile group-containing fluoroelastomer to be prepared
in the present invention, which has nitrile groups at both ends and
is represented by the formula (I):
wherein R.sub.f is a divalent fluoroelastomer chain, is a novel
fluoroelastomer.
It is preferable that the fluoroelastomer chain R.sub.f is a
perfluoroelastomer chain of copolymer or terpolymer represented by
the formula (1): ##STR1## wherein m/(n+p) is 95 to 50/5 to 50, n/p
is 0/100 to 100/0, m+n+p is from 100 to 10,000, R.sub.f.sup.1 is a
perfluoroalkyl group having 1 to 8 carbon atoms, R.sub.f.sup.2 is
--(CF.sub.2 CFYO).sub.q R.sub.f.sup.3, in which R.sub.f.sup.3 is a
perfluoroalkyl group having 1 to 6 carbon atoms, Y is fluorine atom
or a trifluoromethyl group, q is an integer of 1 to 5, or
a perfluoroelastomer chain of terpolymer or tetrapolymer
represented by the formula (2): ##STR2## wherein 1/m/(n+p) is 95 to
35/0 to 30/5 to 35, n/p is 0/100 to 100/0, 1+m+n+p is from 100 to
10,000, R.sub.f.sup.1 and R.sub.f.sup.2 are as defined above.
The fluoroelastomer composition particularly comprising a solid
nitrile group-containing fluoroelastomer having nitrile groups at
ends in the number of more than 1/2 of a total number of end groups
of molecular chains of the fluoroelastomer provides a crosslinked
product having excellent properties.
Further the present invention relates to the process for preparing
an amide group-containing fluoroelastomer which is a starting
substance for the above-mentioned reaction for converting into
nitrile group, by reacting a solid fluoroelastomer having ester
group in a molecular chain thereof, particularly at the end of the
molecular chain with ammonia or aqueous ammonia.
Further the present invention relates to a solid amide
group-containing fluoroelastomer having amide groups at both ends
and. represented by the formula (II):
H.sub.2 NOC--(R.sub.f)--CONH.sub.2
wherein R.sub.f is a divalent fluoroelastomer chain.
Also the present invention relates to a novel process for synthesis
of a nitrile compound which is represented by the formula (IV):
wherein R is a monovalent organic group, and is prepared by
dehydrating an amide compound represented by the formula (III):
wherein R is as defined above, in the presence of COF.sub.2. It is
advantageous to use COF.sub.2 as the dehydrating agent for such a
reaction for converting into nitrile group, from the viewpoint of
yield, low boiling point and easy removal of un-reacted gas after
the reaction.
BEST MODE FOR CARRYING OUT THE INVENTION
Firstly the present invention relates to the process for preparing
a nitrile group-containing fluoroelastomer by converting amide
group contained in a polymer molecular chain of a solid
fluoroelastomer into nitrile group in the presence of a dehydrating
agent.
A fluoropolymer which is a starting material in the process for
preparing the nitrile group-containing fluoroelastomer of the
present invention is firstly (1) in the form of solid. This means
that a liquid fluorooil which is described in the above-mentioned
Polymer Journal, has a relatively low molecular weight (10,000 or
less) and comprises essentially a fluoroether unit, is excluded. As
mentioned above, in case of a liquid fluoropolymer, conventional
dehydrating agents can be used, but in case of a solid
fluoropolymer, non-uniform reaction arises and a desired object
cannot be obtained.
Secondly (2) the fluoropolymer has amide group in a molecular chain
thereof. The amide group may be present in the molecular chain as a
pendant or may be present as end group of the molecular chain. It
is a matter of course that the amide groups may be present in the
both forms. The present invention has an important meaning that it
becomes possible to introduce nitrile group as end group, which has
been so far impossible. Particularly the solid fluoroelastomer
having nitrile groups at both ends, which can be prepared by the
process of the present invention and is represented by the
above-mentioned formula (I) is a novel fluoroelastomer.
In the present invention, an elastomer chain (R.sub.f in the
formula (I)) on a trunk chain portion of the fluoroelastomer does
not change substantially. Examples of the fluoroelastomer chain
R.sub.f are, for instance,
a perfluoroelastomer chain of copolymer or terpolymer represented
by the formula (1): ##STR3## wherein m/(n+p) is 95 to 50/5 to 50,
n/p is 0/100 to 100/0, m+n+p is from 100 to 10,000, R.sub.f.sup.1
is a perfluoroalkyl group having 1 to 8 carbon atoms, R.sub.f.sup.2
is --(CF.sub.2 CFYO).sub.q R.sub.f.sup.3, in which R.sub.f.sup.3 is
a perfluoroalkyl group having 1 to 6 carbon atoms, Y is fluorine
atom or a trifluoromethyl group, q is an integer of 1 to 5,
a perfluoroelastomer chain of terpolymer or tetrapolymer
represented by the formula (2): ##STR4## wherein 1/m/(n+p) is 95 to
35/0 to 30/5 to 35, n/p is 0/100 to 100/0, 1+m+n+p is from 100 to
10,000, R.sub.f.sup.1 and R.sub.f.sup.2 are as defined above, a
non-perfluoroelastomer chain such as
a fluoroelastomer chain of copolymer represented by the formula
(3): ##STR5## wherein m/n is 85 to 60/15 to 40, m+n is from 100 to
10,000,
a fluoroelastomer chain of terpolymer represented by the formula
(4): ##STR6## wherein 1/m/n is 85 to 20/0 to 40/15 to 40, 1+m+n is
from 100 to 10,000,
a fluoroelastomer chain of terpolymer or tetrapolymer represented
by the formula (5): ##STR7## wherein 1/m/(n+p) is 95 to 45/0 to
10/5 to 45, n/p is 0/100 to 100/0, 1+m+n+p is from 100 to 10,000,
R.sub.f.sup.1 and R.sub.f.sup.2 are as defined above, Z.sup.1,
Z.sup.2 and Z.sup.3 are fluorine atom or hydrogen atom
individually, or
a fluoroelastomer chain of terpolymer or tetrapolymer represented
by: ##STR8## wherein 1/m=20/80 to 80/20, 1+m 100 to 10,000,
##STR9## wherein 1/m=80/20 to 50/50, 1+m=100 to 10,000, or
##STR10## wherein 1/m/(n+p) is 85 to 5/5 to 85/10 to 40, n/p is
0/100 to 100/0, 1+m+n+p is from 100 to 10,000, R.sub.f.sup.1 and
R.sub.f.sup.2 are as defined above, and the like.
With respect to the non-perfluoroelastomer chain, conversion into
nitrile group may be carried out after fluorination of the
non-perfluoroelastomer chain with a fluorine gas or the like.
The end group of those fluoroelastomer chains R.sub.f and/or amide
group being present as a pendant are converted to nitrile group in
the presence of a dehydrating agent.
It is preferable that the dehydrating agent is in the form of gas
or liquid because the elastomer is in the form of solid. Examples
of the dehydrating agent in the form of gas are, for instance,
COF.sub.2, COCl.sub.2, SO.sub.3, and the like. Particularly
COF.sub.2 is preferable from the viewpoint of good yield,
relatively moderate reaction conditions and easy treatment. Use of
COF.sub.2 as a dehydrating agent for converting amide group into
nitrile group, i.e. nitrilation of amide group has novelty.
Examples of the dehydrating agent in the form of liquid are, for
instance, acetic anhydride, trifluoroacetic anhydride, ClCO.sub.2
C.sub.2 H.sub.5, and the like. Particularly trifluoroacetic
anhydride is preferable from the viewpoint of a yield. As case
demands, an acid acceptor such as pyridine, triethylamine, or the
like may be used together with those dehydrating agents.
The reaction for converting amide group into nitrile group advances
at a temperature of -20.degree. C. to 200.degree. C. It is
preferable to carry out the reaction under heating, particularly at
a temperature of 50.degree. C. to 150.degree. C. from the viewpoint
of a good yield and a short reaction time. The reaction pressure is
from atmospheric pressure to 5 MPaG, preferably 1 to 2 MPaG. The
reaction time is usually from about 10 hours to about 90 hours. The
reaction can be carried out in the presence or absence of a
solvent. When the solvent is used, for example, a
fluorine-containing solvent (for example, FLORINATE (registered
trademark) series available from SUMITOMO 3M LIMITED), and the like
can be used.
Further the present invention relates to the process for preparing
the amide group-containing fluoroelastomer which is a starting
material for preparing the nitrile group-containing
fluoroelastomer.
The solid fluoroelastomer is usually prepared by radical
polymerization of a fluorine-containing monomer by using a radical
polymerization initiator. There are various compounds known as a
radical polymerization initiator. A lot of general-purpose
initiators, for example, ammonium persulfate, potassium persulfate,
and the like are converted to carboxyl groups by acid treatment to
be carried out when collecting a produced elastomer, thereby giving
a fluoroelastomer having carboxyl groups at ends. A usual method
which can be considered for converting the end carboxyl groups into
amide groups suitable for nitrilation of the present invention is a
method of firstly forming the carboxyl group into an ammonium salt
with ammonia and then heating for dehydration. However when this
method was carried out actually, it was found that ammonia was
evaporated by heating the ammonium salt and the ammonium salt
reverted to carboxyl group. As a result, the inventors of the
present invention have found that even in case of a solid carboxyl
group-containing fluoroelastomer, the carboxyl group can be
converted into amide group effectively by once carrying out
esterification of the carboxyl group and then reacting it with
ammonia or aqueous ammonia in the same manner as in the liquid
fluorooil described in the above-mentioned Polymer Journal. The
obtained solid amide group-containing fluoroelastomer is also a
novel elastomer.
Namely the present invention relates to the method of converting
ester group into amide group by reacting a solid fluoroelastomer
having ester group in a molecular chain, particularly at the end of
the molecular chain with ammonia or aqueous ammonia.
The reaction conditions which can be used are mentioned below.
(1) Reaction Temperature -20.degree. C. to 200.degree. C.,
preferably ordinary temperature to 100.degree. C.
(2) Reaction Pressure Normal pressure to 2 MPaG, preferably 0.1 to
0.5 MPaG
The esterification of the carboxyl group-containing fluoroelastomer
can be carried out under usual esterification conditions, for
example, by a method of reacting the elastomer with an alcohol in
the presence of an acid catalyst, a method of converting into an
acid chloride with thionyl chloride and then reacting with an
alcohol, or the like method.
Examples of the alcohol to be used for the esterification are, for
instance, methanol, ethanol, 1-propanol, 2-propanol, and the like.
Particularly methanol is preferable from the viewpoint of excellent
yield and economy.
As mentioned above, it is known that nitrile group is introduced as
a pendant of a fluoroelastomer. However a nitrile group-containing
fluoromonomer to be used for the introduction of nitrile group is
very expensive, and as a result, the obtained nitrile
group-containing fluoropolymer is expensive.
According to the preparation process of the present invention,
nitrile group can be introduced as a pendant by copolymerizing an
inexpensive carboxyl group-containing fluoromonomer to introduce
carboxyl group as a pendant, and after carrying out esterification
of the carboxyl group as mentioned above to form into amide group,
converting into nitrile group.
Examples of the carboxyl group-containing fluoromonomer to
introduce nitrile group as a pendant are, for instance,
CF.sub.2.dbd.CF[OCF.sub.2 CF(CF.sub.3)].sub.n O(CF.sub.2).sub.m
COOH (n=1 to 2, m=1 to 4), CF.sub.2.dbd.CF(CF.sub.2).sub.n COOH
(n=1 to 5), CF.sub.2.dbd.CFO(CF.sub.2).sub.n OCF(CF.sub.3)COOH (n=2
to 5), CF.sub.2.dbd.CF[OCF.sub.2 CF(CF.sub.3)].sub.n COOH (n=1 to
10), ##STR11## CH.sub.2.dbd.CH(CF.sub.2).sub.n COOH (n=1 to 10),
and the like.
From the viewpoint of good copolymerizability and crosslinkability,
particularly CF.sub.2.dbd.CFOCF.sub.2 CF(CF.sub.3)OCF.sub.2
CF.sub.2 COOH is preferable.
Also the perfluoroelastomer can be prepared from the
non-perfluoroelastomer by fluorinating the non-perfluoromonomer
with a fluorine gas, or the like and then carrying out the
nitrilation because if the non-perfluoromonomer is fluorinated
after the nitrilation, nitrile group is fluorinated.
As mentioned above, the method of converting amide group into
nitrile group in the presence of COF.sub.2 which is a dehydrating
agent is a novel method. This reaction is not a reaction inherent
to the amide group-containing fluoroelastomer and can be applied to
the nitrilation reaction of general amide compounds including low
molecular weight compounds.
Therefore the present invention further relates to the process for
synthesis of the nitrile compound represented by the formula
(IV):
R--CN
wherein R is a monovalent organic group, by dehydrating the amide
compound represented by the formula (III):
wherein R is as defined above, in the presence of COF.sub.2.
Examples of the monovalent organic group represented by R are
various organic groups such as fluoroelastomer chains having a
residue of polymerization initiator or chain transfer agent or a
group derived therefrom at one end thereof, a linear or branched
hydrocarbon group which has 1 to 20 carbon atoms and may be
substituted by one or more halogen atoms, CF.sub.3 CONH.sub.2,
CH.sub.3 CONH.sub.2, C.sub.2 F.sub.5 CONH.sub.2, C.sub.2 H.sub.5
CONH.sub.2, C.sub.6 H.sub.11 CONH.sub.2, C.sub.6 H.sub.5 CONH.sub.2
and C.sub.7 H.sub.15 CONH.sub.2. Also the process can be applied to
a liquid fluorooil mainly comprising a fluoroether unit which is
described in the above-mentioned Polymer Journal.
The reaction conditions for the synthesis may be the same as in the
above-mentioned nitrilation reaction of the solid
fluoroelastomer.
In the present invention, a principal object of introducing nitrile
group is, as mentioned above, to use the nitrile group as a cure
site of the solid fluoroelastomer. Particularly by introducing
nitrile group into at least one end group, preferably into the both
end groups, mechanical properties, heat resistance and compression
set of a crosslinked product can be enhanced.
In the present invention, it is ideal to carry out the nitrilation
perfectly. However in order to enhance characteristics of the
elastomer, the number of nitrile groups may be more than 1/2 of the
total number of end groups of the obtained fluoroelastomer,
preferably 70% or more, particularly preferably 90% or more. Namely
the fluoroelastomer may contain at least one fluoroelastomer chain
having nitrile groups at its both ends. It is preferable that the
remaining cure sites may be carboxyl group, ester group or amide
group.
The present invention further relates to the fluoroelastomer
composition comprising the above-mentioned nitrile group-containing
fluoroelastomer. It is preferable that a crosslinking agent is
contained in the composition.
The nitrile group-containing fluoroelastomer of the present
invention can be crosslinked by triazine crosslinking, oxazole
crosslinking, thiazole crosslinking, imidazole crosslinking, and
the like. Particularly oxazole crosslinking is preferable from the
viewpoint of good compression set, heat resistance and economy.
Examples of the crosslinking agent which can be used are organotin
compounds such as tetraphenyltin and triphenyltin hydride for the
triazine crosslinking; bisaminophenols such as bisaminophenol AF
for the oxazole crosslinking; bisaminothiophenols such as
bisaminothiophenol for the thiazole crosslinking; tetraamines such
as bis( 1,2-phenylenediamine) and
2,2-bis(3,4-diaminophenyl)hexafluoropropane for the imidazole
crosslinking; and the like.
Crosslinked products obtained from the fluoroelastomer of the
present invention are excellent in heat resistance, chemical
resistance, physical properties in normal state, compression set,
plasma resistance, cleanliness, and the like, and can exhibit very
excellent characteristics as various materials for sealing members,
gaskets, hoses and rolls.
The present invention is then explained by means of examples, but
is not limited thereto.
EXAMPLE 1
(1) Synthesis of Polymer Having End Carboxyl Group
A 6,000-ml stainless steel autoclave having no ignition source was
charged with 2,340 ml of pure water, 23.4 g of: ##STR12##
as an emulsifying agent and 0.21 g of disodium hydrogen
phosphate.12H.sub.2 O as a pH control agent, and after replacing
the inside of the system with nitrogen gas sufficiently for
deaeration, the autoclave was heated up to 50.degree. C. with
stirring at 600 rpm. Then perfluoro(methyl vinyl ether) (PMVE) was
introduced so that the inside pressure became 0.3 MPaG (3.0
kgf/cm.sup.2 G) in a gauge pressure and further tetrafluoroethylene
(TFE) was introduced until the inside pressure became 0.4 MPaG (4.1
kgf/cm.sup.2 G). Then 12.3 g of ammonium persulfate (APS) dissolved
in 30 ml of water was introduced with a pressurized nitrogen gas to
initiate a reaction.
When the inside pressure was lowered to 0.34 MPaG (3.5 kgf/cm.sup.2
G) with advance of the polymerization, 6.2 g of PMVE and 5.6 g of
TFE were introduced with the respective self pressures to recover
0.4 MPaG (4.1 kgf/ cm.sup.2 G). After that, lowering of the
pressure to 0.34 MPaG (3.5 kgf/cm.sup.2 G) and introduction of PMVE
and TFE for recovering the pressure were repeated.
At the time when a total amount of TFE and PMVE reached 210 g seven
hours after starting of the polymerization, the autoclave was
cooled and un-reacted monomer was released to give 2,558 g of an
aqueous dispersion having a solid content of 8.0 % by weight.
1,800 Grams of the obtained aqueous dispersion was diluted with
5,400 g of water and slowly added to 4,800 g of an aqueous solution
of 3.5% by weight of hydrochloric acid with stirring. After the
addition, stirring was continued for five minutes, and a
precipitated product was filtrated off. The obtained polymer was
further added to 2 kg of HCFC-141 b, followed by stirring for five
minutes and filtrating off again. After that, the steps of washing
with HCFC-141b and filtrating off were repeated four times,
followed by vacuum drying at 120.degree. C. for 48 hours to give
140 g of polymer.
As a result of .sup.19 F-NMR analysis, contents of TFE and PMVE in
the polymer were 58.6% by mole and 41.4% by mole, respectively.
(2) Esterification of Polymer Having End Carboxyl Group
A 500-ml four-necked flask equipped with a stirrer, thermometer and
reflux tube was charged with 130 g of the polymer prepared in (1)
above, 200 ml of methanol and 2 ml of sulfuric acid, and after
15-hour refluxing, was cooled to room temperature. After filtration
of the reaction solution, 30 ml of methanol was added and washing
by shaking was carried out for 10 minutes. After the washing by
shaking with methanol three times, vacuum drying was carried out at
100.degree. C. for 3 hours to give 130 g of a polymer having, at
the end, ester group obtained by methyl-esterification of carboxyl
group. A conversion of the esterification to the polymer having
ester group at the end was 95.6% which was calculated from IR
absorbance ratio of carbonyl group (1,769 cm.sup.-1) in carboxyl
group before and after the reaction.
(3) Amidation of Polymer Having End Ester Group
After a 200-ml stainless steel autoclave was charged with 130 g of
the polymer having, at the end, ester group which was prepared in
(2) above, the inside pressure of the autoclave was increased up to
0.3 MPa.multidot.G at 60.degree. C. with ammonia gas. After the
reaction was continued in that state for three hours, a remaining
gas was exhausted, followed by vacuum drying at 150.degree. C. for
three hours to give 130 g of a polymer having amide group at the
end. A conversion of the amidation to the polymer having amide
group at the end was 99.2% which was calculated from IR absorbance
ratio of carbonyl group (1,798 cm.sup.-1) in ester group before and
after the reaction.
(4) Nitrilation of the Polymer Having End Amide Group
After a 200-ml stainless steel autoclave was charged with 130 g of
the polymer having, at the end, amide group which was prepared in
(3) above, the inside pressure of the autoclave was increased up to
1.0 MPa.multidot.G at 100.degree. C. with COF.sub.2. After the
reaction was continued in that state for 70 hours, a remaining gas
was exhausted, followed by vacuum drying at ordinary temperature
for 20 hours and then vacuum drying at 80.degree. C. for 26 hours
to give 130 g of a polymer. According to IR analysis of the
obtained polymer, an absorption of nitrile group was recognized at
2,265 cm.sup.-1. A conversion of the nitrilation of the polymer was
84.0% which was calculated from IR absorbance ratio of carbonyl
group (1,752 cm.sup.-1) in amide group before and after the
reaction.
EXAMPLE 2
(1) Synthesis of Polymer Having Carboxyl Group at an End and Side
Chain
A 3,000-ml stainless steel autoclave having no ignition source was
charged with 1,000 ml of pure water, 10 g of: ##STR13##
as an emulsifying agent and 0.09 g of disodium hydrogen
phosphate.12H.sub.2 O as a pH control agent, and after replacing
the inside of the system with nitrogen gas sufficiently for
deaeration, the autoclave was heated up to 50.degree. C. with
stirring at 600 rpm. Then a gas mixture of tetrafluoroethylene
(TFE) and perfluoro(methyl vinyl ether) (PMVE) (TFE/PMVE=25/75 in
mole ratio) was introduced so that the inside pressure became 0.8
MPaG (8.0 kgf/cm.sup.2 G). Then 10 ml of an aqueous solution of
ammonium persulfate (APS) having a concentration of 527 mg/ml was
introduced with a pressurized nitrogen gas to initiate a
reaction.
When the inside pressure was lowered to 0.7 MPaG (7.0 kgf/cm.sup.2
G) with advance of the polymerization, 3.78 g of
CF.sub.2.dbd.CFOCF.sub.2 CF(CF.sub.3)OCF.sub.2 CF.sub.2 COOH (CBVE)
was introduced with a pressurized nitrogen gas. Then 4.7 g of TFE
and 5.3 g of PMVE were introduced with the respective self
pressures so that the inside pressure became 0.8 MPaG (8.0
kgf/cm.sup.2 G). After that, with advance of the reaction, TFE and
PMVE were introduced under pressure in the same manner, and
increasing and lowering of the inside pressure were repeated
between 0.7 MPaG (7 kgf/cm.sup.2 G) and 0.8 MPaG (8 kgf/cm.sup.2
G). At the time when a total amount of TFE and PMVE reached 80 g
4.2 hours after starting of the polymerization, the autoclave was
cooled and un-reacted monomer was released to give 1,091 g of an
aqueous dispersion having a solid content of 7.5% by weight.
1,000 Grams of the obtained aqueous dispersion was diluted with
3,000 g of water, followed by slowly adding to 2,800 g of an
aqueous solution of 3.5% by weight of hydrochloric acid with
stirring. After the addition, stirring was continued for five
minutes, and a precipitated product was filtrated off. The obtained
polymer was further added to 800. g of HCFC-141b, followed by
stirring for five minutes and filtrating off again. After that, the
steps of washing with HCFC-141b and filtrating off were repeated
four times, followed by vacuum drying at 120.degree. C. for 72
hours to give 72 g of a polymer having carboxyl group at the end
and side chain.
As a result of .sup.19 F-NMR analysis, monomer units of the polymer
were TFE/PMVE/CBVE=57.3/41.8/0.9 in % by mole.
According to infrared spectroscopic analysis, a characteristic
absorption of carboxyl group was recognized around 1,774.9
cm.sup.-1 and a characteristic absorption of OH group was
recognized around 3,557.0 cm.sup.-1 and around 3,087.7
cm.sup.-1.
(2) Esterification of Polymer Having Carboxyl Group at an End and
Side Chain
A 500-ml four-necked flask equipped with a stirrer, thermometer and
reflux tube was charged with 130 g of the polymer prepared in (1)
above, 200 ml of methanol and 2 ml of sulfuric acid, and after
15-hour refluxing, was cooled to room temperature. After filtration
of the reaction solution, 30 ml of methanol was added and washing
by shaking was carried out for 10 minutes. After the washing by
shaking with methanol three times, vacuum drying was carried out at
100.degree. C. for 3 hours to give 130 g of a polymer having, at
the end and side chain, ester group obtained by
methyl-esterification of caboxyl group. A conversion of the
esterification to the polymer having ester group at the end and
side chain was 95.8% which was calculated from IR absorbance ratio
of carbonyl group in carboxyl group before and after the
reaction.
(3) Amidation of Polymer Having Ester Group at an End and Side
Chain
After a 200-ml stainless steel autoclave was charged with 130 g of
the polymer having ester group at the end and side chain and
prepared in (2) above, the inside pressure of the autoclave was
increased up to 0.3 MPa.multidot.G at 60.degree. C. with ammonia
gas. After the reaction was continued in that state for three
hours, a remaining gas was exhausted, followed by vacuum drying at
150.degree. C. for three hours to give 130 g of a polymer having
amide group at the end and side chain. A conversion of the
amidation to the polymer having amide group at the end and side
chain was 99.4% which was calculated from IR absorbance ratio of
carbonyl group in the ester group before and after the
reaction.
(4) Nitrilation of Polymer Having Amide Group at an End and Side
Chain
After a 200-ml stainless steel autoclave was charged with 130 g of
the polymer having amide group at the end and side chain and
prepared in (3) above, the inside pressure of the autoclave was
increased up to 1.0 MPa.multidot.G at 100.degree. C. with
COF.sub.2. After the reaction was continued in that state for 70
hours, a remaining gas was exhausted, followed by vacuum drying at
ordinary temperature for 20 hours and then vacuum drying at
80.degree. C. for 26 hours to give 130 g of a polymer having
nitrile group at the end and side chain. A conversion of the
nitrilation of the polymer having nitrile group at the end and side
chain was 83.4% which was calculated from IR absorbance ratio of
carbonyl group in the amide group before and after the
reaction.
EXAMPLE 3
A dried 25-ml stainless steel bomb was charged with 0.83 g of
perfluorooctanoic acid amide (available from PCR Inc.) and 1 ml of
diethylene glycol dimethyl ether, and after pressure reduction to 5
mmHg, the bomb was sealed. Subsequently the inside pressure of the
bomb was increased to 1.0 MPaG with COF.sub.2 and the reaction was
continued at room temperature. 24 Hours after, a remaining gas was
exhausted and a reaction mixture was neutralized with 10% aqueous
solution of NaHCO.sub.3 to a neutral level to separate into two
phases. From the lower phase, 0.71 g of yellow oily substance was
obtained. According to gas chromatography and GC mass spectrum
analysis (column: SE-30), production of C.sub.7 F.sub.15 CN was
recognized. A purity of the crude product was 89.5% and a yield of
the reaction was 80.1%.
Industrial Applicability
According to the present invention, a solid fluoroelastomer having,
at the end, nitrile group functioning as a cure site and an
economical preparation process thereof can be provided. Crosslinked
products obtained from such a fluoroelastomer are excellent
particularly in heat resistance, solvent resistance, chemical
resistance, compression set, cleanliness, and the like, and can
exhibit very excellent characteristics as various materials for
sealing members, gaskets, hoses and rolls in the fields of
semi-conductor production apparatuses, transportation means such as
car, aircraft, rocket and vessel, chemical industries such as
chemical plant and medical instruments and machinery such as
developing machine, printing machine and coating facilities.
* * * * *